Former Juventus and Chelsea striker Mutu lands coaching job with his old team
The Romanian Football Federation (FRF) confirmed Mutu in the job on Wednesday, after successful talks with president Razvan Burleanu.
It means the 41-year-old former Juventus, Fiorentina and Chelsea forward assumes control of a side who are in the frame to qualify for the Euro 2021 finals.
"I feel honoured, it is a big responsibility for me," said Mutu, quoted on the FRF website.
The Romania Under-21 side were semi-finalists at Euro 2019, where they beat Croatia and England and drew with France before losing to Germany in the semi-finals.
He takes over from Mirel Radoi, who in November was rewarded for his success by being appointed head coach of the senior Romania team.
Mutu said: "I'm coming after Mirel Radoi, who made history with the national Under-21s, and this motivates me even more. This is a talented new generation, this campaign started well. The objective is qualification for the Euros."
Mutu has previously had a short spell as boss of Romanian club side Voluntari and has also coached the Al Wahda reserve team in Abu Dhabi.
The Romania Under-21 side sit second in their Euro 2021 qualifying group, behind leaders Denmark.